<html>
    <head>
        <meta charset="UTF-8">
        <title>demo</title>
    </head>
    <body>
        <style type="text/css">
            .div1{  width: 100%; height: 100%;} 
            .div2{ width: 90%; height: 90%; background-color: green;}

            /*.div22{
                margin-left: 30px;margin-top: 30px;
            }*/
        </style>

        <div class="div1">
            <div class="div2 div22">

            </div>
        </div>

    </body>
</html>